<style>
    .table-container {
        background-color: transparent;
        color: white;
        width: 100%;
        height: 270px;
        padding: 20px;
        text-align: center;
        table-layout: fixed;

    }

    .table-container td{
        border: 1px white solid;
        border-radius: 5px;
    }
</style>
<table class="table-container">
    <tr>
        <td></td>
        <td onclick="piano.play(PianoFreq[1])">1</td>
        <td></td>
    </tr>
    <tr>
        <td onclick="piano.play(PianoFreq[2])">2</td>
        <td onclick="piano.play(PianoFreq[3])">3</td>
        <td onclick="piano.play(PianoFreq[4])">4</td>
    </tr>
    <tr>
        <td onclick="piano.play(PianoFreq[5])">5</td>
        <td onclick="piano.play(PianoFreq[6])">6</td>
        <td onclick="piano.play(PianoFreq[7])">7</td>
    </tr>
</table>